Seasonal variations of PM10 and TSP in residential and industrial sites in an urban area of Kolkata, India.

The objective of the study is to investigate seasonal and spatial variations of PM10 (particulate matter with aerodynamic diameter less than or equal to 10 microm) and TSP (total suspended particulate matter) of an Indian Metropolis with high pollution and population density from November 2003 to November 2004. Ambient concentration measurements of PM10 and TSP were carried out at two monitoring sites of an urban region of Kolkata. Monitoring sites have been selected based on the dominant activities of the area. Meteorological parameters such as wind speed, wind direction, rainfall, temperature and relative humidity were also collected simultaneously during the sampling period from Indian Meteorological Department, Kolkata. The 24 h average concentrations of PM10 and TSP were found in the range 68.2-280.6 microg/m3 and 139.3-580.3 microg/m3 for residential (Kasba) area, while 62.4-401.2 microg/m3 and 125.7-732.1 microg/m3 for industrial (Cossipore) area, respectively. Winter concentrations of particulate pollutants were higher than other seasons, irrespective of the monitoring sites. It indicates a longer residence time of particulates in the atmosphere during winter due to low winds and low mixing height. Spread of air pollution sources and non-uniform mixing conditions in an urban area often result in spatial variation of pollutant concentrations. The higher particulate pollution at industrial area may be attributed due to resuspension of road dust, soil dust, automobile traffic and nearby industrial emissions. Particle size analysis result shows that PM10 is about 52% of TSP at residential area and 54% at industrial area.